This invention generally relates to an article formed of an iron base powder metal. More specifically, this invention relates to an article formed using an iron phosphorous powder metal compressed and then copper infiltrated during the sintering process.
Powder metal materials are used to produce many devices, such as medical, automotive and aerospace devices that have a need for net-shaped components that may be simple or complex in shape. Powder metal components are typically produced through a sintering process of the metal powders. The composition and processing of the material are one of the most significant factors in the determination of the physical properties that the finished powder metal component will exhibit.
There have been many combinations of powder metal materials developed that exhibit various mechanical properties necessary for different applications. However, to achieve superior mechanical properties, powder metal components have been manufactured using a variety of processes such as powder forging, double pressed double sinter, etc are required. However, components made using any of the above-mentioned processes are prohibitively expensive for many production uses.
In view of the foregoing, there is a need to provide a powder metallurgy material that yields improved mechanical performance. Preferably, the metal powder component is manufactured using a single press and single sinter process. It is also preferable that the article formed from the present invention when compared with materials made from similar process having a matrix density of less than or equal to 7.3 g/cc, exhibit superior mechanical and physical properties.
The present invention is a new powder metallurgy material with superior mechanical properties. The specific combination of materials such as phosphorus iron infiltrated with copper during sintering creates a composite with significantly better mechanical properties than current powder metal composites or alloys also manufactured using the single press and single sinter process. The superior physical and mechanical properties of the component made using the present invention and the amount of copper infiltrated into the matrix for a given matrix density suggest that the addition of phosphorous to the iron based powder infiltrated with copper has a chemical and kinetic synergy. It is believed that phosphorous is a flux that aids copper wetting to the iron and improves copper penetration into the porosity of the matrix. Decreased porosity and rounded pores improves impact and elongation properties while the copper increases the iron matrix""s strength. Normally carbon would be used to increase iron strength, however, with the phosphorous present, a significant amount of carbon would decrease impact strength and elongation properties. Therefore, diffused copper increases the iron matrix""s strength instead of carbon in the invention material. It is also theorized that when using ferro-phosphorous powder as a source of phosphorous, the liquid phase sintering, may act as a transport mechanism and improve copper infiltration. It is also believed that the phosphorous increases copper wetting of the matrix particles.